CompletableFuture.allof() 获取空指针异常

Question

我的结构类似于下面的代码块。不知何故，我在 CompletableFuture.allOf 方法中得到 nullpointerException： 这里可能有什么问题？ 谢谢..

List<CompletableFuture<String>> completableFutures = new ArrayList<>();

for(Classx list : request.getlist()) {
    switch (list.getCases()) {
        case 1:
            completableFutures.add(asyncProcess(list));
            break;
        case 2:
            completableFutures.add(asyncProcess2(list));
            break;
    }
}
CompletableFuture<Void> allFutures = CompletableFuture.allOf(completableFutures.toArray(new CompletableFuture[0]));


@Async
public CompletableFuture<String> asyncProcess(Classx list) {
    try{
        //..some codes
    } catch(Exception e){
        //..some codes
    }
    return CompletableFuture.completedFuture(x.getX());
}


@Async
public CompletableFuture<String> asyncProcess2(Classx list) {
    try{
        //..some codes
    } catch(Exception e){
        //..some codes
    }
    return CompletableFuture.completedFuture(x.getX());
}

错误信息是：

java.lang.NullPointerException
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1306)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1305)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1305)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1305)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1305)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1305)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1305)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1305)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.allOf(CompletableFuture.java:2225)

当我按如下方式更改代码时，它会引发相同的错误。

CompletableFuture allFutures = CompletableFuture.allOf(completableFutures.toArray(new CompletableFuture[completableFuture.size()]));

Answer 1

查看CompletableFutre.andTree

的源代码，似乎当传入数组的元素为

null

时抛出此异常。在您的

return

函数之一中必须有一些额外的

asyncProcees

语句可以返回

null

。